Chapter on Tayammum and Its Rules

As for what was narrated by Muhammad ibn Ali ibn Mahboub, from Al-`Ubaydi, from Hammad ibn Isa, from Hariz, from Muhammad ibn Muslim, who said: I asked Abu Abdullah عليه السلام about a man who becomes junub during travel and finds nothing but snow or frozen water. Imam عليه السلام said: "It is considered a state of necessity; he should perform tayammum. However, I do not advise him to return to this land that endangers his religion."